In the production of semiconductor workpieces, numerous materials layers are deposited on a substrate during device fabrication. The deposited layers may have different thermal expansion coefficients and contain contaminants, defects or undesired microstructures, which all have negative effects on the semiconductor workpiece quality. Commonly a thermal treatment process is required to reduce or eliminate these negative effects before the semiconductor workpieces are transferred to the next fabrication step. Other deposited layers may need a thermal treatment process to improve their physical and electrical properties. For example freshly deposited copper films in copper interconnect process need an anneal process to reduce their resistivity and stabilize grain structures before the subsequent chemical mechanical polishing step. Conventional thermal treatment is realized with a single conductive, convective or radiant heat source. The single side thermal treatment often leads to a large initial temperature gradient along the thickness of the semiconductor workpiece in the direction perpendicular to its surface. Such a temperature gradient, together with difference in thermal expansion coefficients among the layers, result in stress mismatch and deforms the semiconductor workpiece, commonly known as “bowing”. Severe bowing can cause device failure and yield loss. In practice the semiconductor workpiece is usually pre-heated for a period of time before the thermal treatment at the desired temperature to reduce bowing. Therefore the time of thermal process is greatly increased and the process throughput is limited. Similarly lengthy cooling step can also limit the process throughput. An apparatus and a method for thermal treatment of semiconductor workpieces with smaller temperature gradient and higher efficiency are desired.